Dairy cattle require large amounts of water daily, as free drinking water and moisture in the feed. The major factors that influence water intake are: 1) dry matter intake, 2) milk production level, 3) dry matter content of the diet, 4)temperature and environment, and 5) sodium intake. Several equations exist that predict water intake; perhaps the most accurate is from the Dairy NRC (2001) and is readily available on-line.

It’s best to actually measure water intake on-farm using water meters or some other method, but this equation can be used to provide reasonably accurate estimates of expected water intake, for instance, when designing new barns and calculating needed water capacity. An excellent website for assessing water quality and requirements is “WaterForCows.com” I have found the water model and information on this web site to be highly user friendly – plus it uses the NRC water intake model.

Peak water intake is usually associated with feeding and milking. Feed and water resources should be located close together to encourage both feed and water consumption. Cows in tie stalls drink about 14 times daily whereas cows in loose housing only drink approximately 7 times daily. Most water is consumed during daylight hours, and the rate of water consumption can vary between 8.8 (bowl or cup) and 33 (tank or trough) pounds per minute.

Cows drink a lot of water quickly and the on-farm system must be designed to handle these water needs. For instance, 6 cows at a water tank drinking at one time can consume 2 to 4 gallons per minute each, so in one minute they consume about 12 to 24 gallons. The best water systems can provide up to 33 gallons per minute flow rate into the tank.

Dominance and social interactions may play a large role in determining how well cows are able to drink. Some studies have shown that with a shared water bowl, the subordinate cow drinks less water and consumes less feed than the dominant cow. Other research has found that when cows share a common water bowl, both the dominant and the subordinate cow lose water intake and milk production. Presumably this response is because the dominant cow spends so much time guarding the water bowl that it interferes with her ability to eat, drink, and rest normally. Regardless of which situation occurs on-farm, the net result is lost production.

Generally at least 20% of cows in a group should be able to drink at the same time. Water tank perimeter should be at least 2 in/cow, but preferably 4 to 5 in/cow. Recent work from the University of Guelph found that milk yield increases by about 2 lb/d for every 1 in/cow increase in water trough space within a range of 1.5 to 5 in/cow.

Kansas State University research found that the water tank most heavily used by cows in a typical free-stall pen is the tank located in the middle cross-over alley. The second most heavily used tank is located by the pen exit, and the least used tank is often the one located at the end cross-over alley furthest from the pen exit gate. We need to keep this in mind as we design

facilities and consider cross-over alley width and water space availability.

The bottom line is that water is the most critical nutrient to the dairy cow and we must ensure that they have continuous access to clean water, delivered in a system that allows natural drinking behavior and water consumption.